If At is the area of steel cross-section, t is working stress, L is width of road and W is weight of slab per square metre, the spacing of the tie bars for a longitudinal joint, is

Highway engineering (also known as roadway engineering and street engineering) is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construction, operation, and maintenance of roads, highways, streets, bridges, and tunnels to ensure safe and effective transportation of people and goods. (Source: Wikipedia)